In the wood working industry and the like, it is a common practice to align the cutting edges of knives on planers to the knife cutter head. The cutter heads, cylindrical in shape are of various diameters, dependent on the manufacturer. Each cutter head has multiple knife blades, each knife blade aligned to the same cutting depth from the surface of the cutter head. A misaligned knife blade, one that is of a shallower cutting depth from the surface of the cutter head may do all the cutting (because its cutting edge is higher than the other cutting edges) and one that is of a deeper cutting depth from the surface may not do any cutting at all (because its cutting edge does not contact with the surface to be planed). In either event, there results in poor quality planed surfaces and uneven knife wear necessitating more frequent replacement of the cutting knives.
Further, as the cutter heads rotate at high revolutions per minute, any shift in the balance of the cylindrical cutter head may pose a danger to an operator. Correctly positioned knives provide better balance and do not create unnecessary and dangerous conditions for an operator. The smooth rotation of the cylindrical cutter head also ensures a smooth planed surface and uniform knife wear.
The cutting knives are also removed periodically for maintenance, including sharpening, and for replacement of worn cutting knives. The reinstallation of the cutting knives after maintenance or replacement is time intensive in that it is important to correctly align all cutting knives to the same cutting depth. The physical shape of the cutter head, being cylindrical, make such procedures difficult and time consuming.
U.S. Pat. No. 5,020,228 to Hessenthaler (Jun. 4, 1991) teaches a jig for aligning cutter blades to a cutter head comprising a magnetic bar adjustably suspended over a knife blade, set by screws, supported by a pair of arcuate members at substantially opposing ends of the magnetic bar. The arcuate members are pivotally supported by substantially parallel base bars that rest on the rotors. The Hessenthaler jig can be used with a variety of rotors of varying diameters due to the pivotally supported arcuate members. However, there is no mechanism to align the jig with the knife blade consistently and the base support bars do not allow for height adjustability of the jig itself.
U.S. Pat. No. 1,653,048 to Kelly (Oct. 1, 1925) teaches an arcuate jig gauge that rests on top of a rotor. It has an adjustable element that aligns on top of a knife blade and is height adjustable. However, '048 to Kelly does not teach the height adjustability to aid in positioning the jig over a knife blade, but rather to avoid debris that may be on the surface of the rotor. Further, this technology is not accommodating of varying diameters of a rotor.
U.S. Pat. No. 4,519,142 to Parker (May 28, 1985) discloses a blade height calibration device. It comprises a base member, a vertical support member and an arcuate head having an adjustable set screw. A cutter head is placed within the device, and a portion of the arcuate head rests on the cutter head, forming a space to accommodate a knife blade. This technology teaches a point of contact with the rotor by way of the vertical support member and a portion of the arcuate head. Disadvantageously, '142 to Parker cannot accommodate rotors or varying diameters, as the vertical member is in a fixed position and of a fixed size.
U.S. Pat. No. 2,496,800 to Larkins (Nov. 5, 1947) discloses a pair of apparatus that are placed at each opposing ends of a cutter head. Each apparatus disclosed is individually manipulated and supported independently on the cutter head by a member, having a cavity therein to accommodate the knife blade. The height of the member is not adjustable, and the position of the apparatus cannot be consistently aligned respecting the position of the knife blade.
Therefore, there is a need for a jig or adjustment tool that allows for quick, easy, and simple alignment of cutting knives on a planar cutting head that is height adjustable. Further the jig would permit reproducible alignment of the knife blades position relative to the rotary cutter head.
There is also a need for an adjustment jig that is capable of reproducing a consistent alignment for each knife blade on a rotary cutter head and for reproducing a consistent alignment of all the knife blades on a rotary cutter head.
There is also a need for a jig or adjustment tool that is universal for use on most available rotary cutter heads.